NFG I know it's a delicate activity and if you mess up and get blacklisted it's sometimes almost impossible to be removed from a blacklist. Some mail providers like Outlook are quite aggressive with spam filters. One thing that Postmark recommends is to "warm up" an IP address when you start sending emails, so that you don't exceed mail providers limits and get immediately blacklisted. Postmark doesn't actually recommend using a dedicated IP address even with their own service, because they see that deliverability is better when you use a shared IP address that has constructed a good reputation over the years.
Glad to hear that everything's working fine in your case though 🙂 I was just pointing out that there are a lot of things to take care of when you want to send email on your own. And if you don't get them right from the start, you might need to start from scratch at some point, even by changing the domain...
